Adhesion of Escherichia coli onto oxide minerals - extended dlvo theory and Flotation behaviour

The adhesion behaviour of Escherichia coli to three oxide minerals (quartz, hematite and corundum) was investigated experimentally. A strain of E. coli was used that contains genes encoding a protein involved in silica precipitation. Maximum cell adhesion was observed at pH <4.3 for quartz and at pH 4.5 - 8.5 for corundum. Cell adhesion to hematite remained low at all pHs. Microbe-mineral adhesion was assessed with an extended DLVO theory approach. The essential parameters used to calculate the energy of the microbe-mineral interaction (Hamaker constants and acid-base components) were experimentally determined. The extended DLVO approach can be used to explain the results of the adhesion experiments. The effect of E coli on the floatability of the three oxide minerals was determined. Our results showed that Ecoli can act as a selective collector for quartz at acidic pHs, with 90 per cent of the quartz floated at 1.5 × 109 cells/mL. However, only 9 per cent of hematite and 30 per cent of corundum was floated under similar conditions. Using E coli and no reagents, it was possible to separate quartz from a hematite-quartz mixture with a Newton's efficiency of 0.7. Quartz was removed from a corundum mixture by E coli with a Newton's efficiency of 0.6.